Method and an arrangement for producing basic fastener tab material, such basic starting material, and fastener tabs

ABSTRACT

A method of producing basic starting material for the manufacture of fastener tabs intended for joining the side portions of the front and rear parts of an absorbent article. The method includes stretching a first sheet of elastic material in a first direction; applying a second and third sheet of material onto respective opposite sides of the first sheet; fastening the three material sheets together in at least two mutually separated zones that extend parallel with each other in one direction perpendicular to the first direction; dividing the first sheet in each region between two zones along a line lying therebetween, whereby the first sheet contracts to a non-stretched state, and thereafter fastening the sheets together in each region between two zones. The invention also relates to an arrangement for carrying out the method, to starting material for producing fastener tabs, and to such a tab.

This application is a division of co-pending application Ser. No.10/286,905, filed on Nov. 4, 2002, the entire contents of which arehereby incorporated by reference.

FIELD OF INVENTION

The present invention relates to a method and to an arrangement forproducing basic starting material for the production of fastener tabsthat are intended to fasten together the side portions of absorbentarticles, such as diapers or like articles that include a front part, aback part and an intermediate crotch part, so that the article will havea pants-like configuration. The invention also relates to such basicstarting material and to a fastener tab produced from such material.

BACKGROUND OF THE INVENTION

Absorbent article fastener tabs used to fasten together the sideportions of articles so that the article will have a pants-likeconfiguration when worn are known in many different varieties. Forinstance, the tabs may be of a mechanical type that includes hooks ofthe touch-and-close fastener type or some like type, as described inEP-A1-0 235 014, for instance. Fastener tabs of this type, however, areexpensive and difficult to apply at fast speeds in the manufacture ofabsorbent articles. Such tabs have therefore had limited use.WO-A1-95/05140 describes a fastener tab manufacturing method which issaid to avoid these problems.

Other types of fastener devices that are more suited for application athigh speeds are known to the art. For instance, it is known to provide adiaper with pressure-sensitive tape for fastening the diaper around thewaist of a wearer, therewith fastening the front and back side of thediaper together to obtain a pants-like configuration. These tapes areoften made of paper material and are therefore usually relatively rigid.These tapes are also often provided with some form of protective filmthat must be removed prior to use.

Elastic fastener devices are also known in the present context. Forinstance, U.S. Pat. No. 3,800,796 describes a disposable diaper thatincludes semi-elastic fastener tabs. The fastener tabs may compriseelastic material that forms an elastic zone surrounded by non-elasticmaterial that forms two non-elastic zones, or may alternatively comprisesolely elastic material that has been made non-elastic at its edgeregions in some suitable manner. One of these non-elastic zones of thefastener tabs is fastened to the diaper and the other is provided withan adhesive substance, for instance.

TECHNICAL PROBLEMS

One problem resides in the ability of producing both left-hand andright-hand fastener tabs simultaneously, which is desirable since pairsof left-hand and right-hand fastener tabs are often fastenedsimultaneously to mutually sequential absorbent article blanks in thecontinuous manufacture of such articles. Furthermore, it shall bepossible to produce absorbent articles provided with such fastener tabsat high production rates. Difficulties may be experienced in applyingglue and other adhesive substances.

The fastener tabs must also be soft, partially air permeable and mustnot chafe the skin of the wearer.

Furthermore, it is desirable that elastic fastener devices will includea “stop function” that has a distinct stop which “informs” the user orthe carer when the elastic part has been stretched to a maximum, i.e.includes casing material that prevents further stretching of the elasticsheets or layers. This can be achieved with stretched elastic fastenedto a non-elastic casing material. Alternatively, the casing material canbe pleated and fastened to a smooth elastic material, which may beeither in a stretched or a relaxed state.

Against this background of the aforesaid problems, a preferred methodhas been a laminating method in which the elastic is stretched and thecasing materials are smooth, and in which the casing materials arejoined together, suitably by heat welding or ultrasound welding.

EP-A1-0 494 941 describes a method of producing an elastic material, byjoining two sheets of non-stretchable material that enclose a stretchedelastic sheet, through the medium of perforations in the elastic sheet.This document also discloses that zones of different elastic propertiescan be produced through the medium of different perforation patterns andthat non-elastic zones can also be produced, wherein the non-elasticzones are parts that were originally elastic but that have been “killed”by intensive heat treatment or ultrasound welding. The resultantnon-elastic zones are relatively dense, although they are air-permeableto some extent. Furthermore, the intensive treatment has a negativeeffect on the casing materials, which tend to become hard. The desiredsmooth surface is lost and the hard edges that are formed are veryliable to chafe the wearer's skin when coming into contact therewith.Further examples of similar elastic material are found inWO-A1-92/15444, for instance.

It is difficult to pleat casing materials prior to being fastened to theelastic material, because of the high precision required. Thisdifficulty is more pronounced at high manufacturing rates. Theapplication of glue becomes difficult. When the materials are notthermally miscible, problems also occur in heat sealing processes.

There are thus problems which known technology has been unable to solve.

The above problems are essentially avoided completely by the presentinvention. The object of the invention is to provide a method andarrangement for producing basic starting material for the production offastener tabs that have different degrees of stretchability in differentdirections and that are intended for fastening absorbent articles aroundthe wearer's waist, and that can be produced in pairs at high productionrates, and with which the use of adhesive agents can be limited. Thefastener tabs shall also fulfil the requirement of softness, shall beair permeable and not cause chafing of the skin.

SUMMARY OF THE INVENTION

These objects are achieved in accordance with the invention with amethod of producing basic starting material for the production offastener tabs which are intended to join together the side-parts of thefront and back portions of absorbent articles that include a front part,a back part and an intermediate crotch part so as to impart a pants-likeconfiguration to said article, said method being characterised by thesteps of

stretching a first sheet of elastic material in a first direction;

applying a second and a third sheet of material on respective oppositesides of the first sheet;

fastening the three sheets of material together in at least two mutuallyseparate zones that extend parallel to each other in a second directionperpendicular to said first direction;

dividing the first sheet in each region between two zones along a linethat lies between said zones, wherewith the first sheet in each regionbetween two zones contracts to a non-stretched or relaxed state, andthereafter

fastening the three sheets of material together in each region betweentwo zones.

In one preferred embodiment of the invention, the sheets of material arefastened together in each region between two zones in which the secondand third sheets are fastened to the first sheet with said sheet in astretched state and with the first sheet stretched in said zones.

In one alternative, the first sheet of material may be caused tocontract to an unstretched state prior to the sheets being fastenedtogether in each region between two zones, in which the second and thirdsheets are fastened to the first sheet with said sheet in a stretchedstate.

In one preferred embodiment of the invention, the first, second andthird sheets of material are fastened together in two edge regions thatextend in said second direction and that extend in said first directionoutwardly of the nearest zone, in which the second and third sheets arefastened to the first sheet with said sheet in a stretched statesubsequent to having caused said first sheet to contract to anunstretched state in the zones in which the second and third sheets havebeen fastened to the first sheet with said sheet in a stretched state.

Division of the first sheet in each region between two zones in whichthe second and third sheets are fastened to the first sheet with saidsheet in a stretched state is effected by providing a line ofperforations in the first sheet, wherein the spacing between saidperforations is so small that the contracting force in the stretchedfirst sheet is sufficient to pull the first sheet apart in the regionbetween two mutually sequential perforations.

The invention also relates to an arrangement for the continuousproduction of basic starting material for the manufacture of fastenertabs that are intended to join the side-parts of the front and rearportions of absorbent articles that include a front part, a rear partand an intermediate crotch part, so as to impart a pants-likeconfiguration to said article, said arrangement being characterised bymeans for advancing a first web of elastic material through saidarrangement in one feed direction; means for stretching the first webtransversely to the feed direction; means for applying a second and athird web of material onto respective opposite sides of said first web;means for fastening the combined webs together in at least two mutuallyseparated zones that extend parallel with one another in said feeddirection; means for dividing the first web in each region between twozones in which the three webs are fastened together with the first webin a stretched state, along a line that lies between said zones, whereinthe first sheet of material in each region between two zones contractsto an unstretched or relaxed state; and means for fastening the webstogether subsequent to the division of the first web in each regionbetween two zones in which the three webs are fastened together with thefirst web in a stretched state.

According to one preferred embodiment, the arrangement includes meansfor bringing the stretched first web to an unstretched state, anddownstream means in the feed direction for fastening the three webstogether in the edge regions that extend in the feed direction outwardlyof the transversely outermost zones in which the three webs of materialare fastened together with the first web in a stretched state.

The means for bringing the stretched first web of material to anunstretched or relaxed state are preferably located downstream of themeans for fastening the webs together in each region between two zonesin which the three webs are fastened together with the first web in astretched state, subsequent to having divided said first web.Alternatively, said means may be located immediately downstream of saidmeans for dividing the first web of material in each region between twozones in which the three webs are fastened together with the first webin a stretched state.

The means for fastening said webs together will preferably have the formof an ultrasound welding unit or a heat welding unit. It is alsopossible to use different types of means for the different fasteningoperations.

The means used to fasten the three webs together, with the first web ina stretched state, may alternatively have the form, of a gluing unit.The means for dividing the first web in each region between two zones inwhich the three webs are fastened together with the first web in astretched state, along a line that lies between said zones, may comprisea perforating device that perforates the first web. In the preferredembodiment, the perforating device is an ultrasound unit adapted toperforate the first web of material and to fasten the second and thirdwebs together through the holes or openings created in the first web insaid perforating process.

The invention also relates to a basic starting material for theproduction of fastener tabs which together function to fasten togetherthe side-parts of an absorbent article that includes a front part, arear part and an intermediate crotch part, so as to impart to thearticle a pants-like configuration, wherein the basic starting materialhas a length and a width, characterised in that said basic startingmaterial includes at least two elastic zones that extend in thelongitudinal direction of said material and that are mutually separatedtransversely by an intermediate non-elastic zone.

In one preferred embodiment, the elastic material extends from theelastic zones slightly into each non-elastic zone and the ratio betweenthe transverse extension of the elastic zones in a maximum stretchedstate and in a relaxed state is smaller than or equal to the ratio ofthe transverse extension of the intermediate non-elastic zone to the sumof the transverse extension of those pieces of elastic material thatextend into said zone.

The elastic zones include a layer or sheet of elastic material which ismounted in a stretched state between two sheets of material and fastenedthereto, either directly or indirectly, said two sheets extending overeach elastic and non-elastic zone. By “fastened directly” is meant thatthe sheets, or layers, are directly fastened to each other as by gluingor ultrasound welding for instance, whereas by “fastened indirectly” ismeant that the two sheets or layers are fastened together viaperforations in the intermediate sheet, in the manner described in theaforesaid EP-A1-0 404 941. At least one of the two sheets of materialbetween which an elastic sheet is mounted in the elastic zones iscomprised of a generally non-stretchable material, preferably a nonwovenmaterial that will conveniently include thermoplastic fibres. In oneadvantageous variant, the two sheets of material between which anelastic sheet is mounted in the elastic zones are comprised of nonwovenmaterial and both have mutually the same weight per unit area. In onepreferred embodiment, both of said sheets are comprised of nonwovenmaterial and have mutually different weights per unit area, wherewithone has a weight per unit area of 5-50 g/m.sup.2 while the other has aweight per unit area of between 10-80 g/m.sup.2. In one particularlypreferred variant, at least one of the nonwoven sheets or layers is aspunbond nonwoven. Each elastic zone includes a sheet of elastic film,elastic foam, elastic net or a laminate that includes at least oneelastic component.

The invention also relates to a fastener tab which is intended to befastened to one side part of an absorbent article that includes a frontpart, a rear part and an intermediate crotch part, so as to joinmutually coacting side-parts of the front and rear part of the articleand therewith give the article a pants-like configuration, wherein thefastener tab has a user end and a manufacturer end and is characterisedin that it includes a layer of elastic material which is fastened in astretched state to two layers or sheets of generally unstretchablematerial, either directly or indirectly; in that the two unstretchablelayers extend beyond the elastic layer so as to form an unstretchableend part; in that the elastic layer extends in a relaxed state slightlyinto the unstretchable end-part; and in that fastener means are mountedin the unstretchable end-part in the user end of one of the twounstretchable layers.

In one preferred embodiment, the unstretchable layers or sheets arecomprised of nonwoven material of mutually different weights per unitarea, and the fastener means are attached to the outside of the nonwovensheet that has the lowest weight per unit area.

Finally, the invention relates to an absorbent article, such as a diaperor an incontinence protector, which is characterised by including afastener tab according to the above.

Basic starting material produced in accordance with the method and bymeans of the inventive arrangement thus enables left-hand and right-handfastener tabs to be produced at a high production rate while obtaining asoft and comfortable product.

An important feature of the fastener tabs and the basic startingmaterial is that the elastic zone presents a clear stop in a maximumextended or stretched position. Furthermore, the non-elastic zoneoutwardly of the elastic zone on the fastener tabs and between theelastic zones of the basic starting material respectively shall besmooth so as to facilitate application of fastener elements, such asmale fastener elements or female fastener elements in said zone. Thebasic starting material produced is continuous. A continuous web ofmaterial is mainly beneficial from a process/technical aspect, althoughnot necessarily so.

Further preferred embodiments will be apparent from the detaileddescription of preferred embodiments given below with reference to theaccompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described in more detail with reference to theaccompanying drawings, in which

FIG. 1 illustrates schematically and from above an embodiment of aninventive arrangement for producing basic fastener tab material,although the ultrasound welding unit used in the arrangement is notshown in this Figure;

FIG. 2 is a partially cut-away view from one side of the arrangementshown in FIG. 1, and shows schematically the ultrasound welding unitused in the arrangement;

FIGS. 3-8 are cross-sectional views taken on the lines III-III to andincluding VIII-VIII in FIG. 1;

FIG. 9 is a cross-sectional view of devices for firmly holding a web ofelastic material included in the arrangement shown in FIG. 1;

FIG. 10 illustrates a counterpressure or anvil roller in a web dividingdevice included in the arrangement shown in FIG. 1;

FIG. 11 illustrates another embodiment of a basic starting materialaccording to the invention;

FIG. 12 illustrates a first embodiment of an inventive basic startingmaterial produced with the arrangement shown in FIGS. 1-10;

FIG. 13 is a schematic illustration of the manufacture of fastener tabsfrom the material shown in FIG. 12;

FIG. 14 illustrates a fastener tab according to one embodiment of theinvention; and

FIG. 15 is a schematic illustration of a diaper provided with inventivefastener tabs.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

FIGS. 1-10 illustrate schematically one embodiment of an inventivearrangement of devices for producing basic starting material for themanufacture of elastic fastener tabs intended for attachment toabsorbent articles, such as diapers or incontinence protectors, so as toimpart a pants-like configuration to the article when the article isdonned by a wearer.

A first web 1 of elastic material is fed from a storage reel 2 in thefeed direction M and moved into the inventive arrangement. Upon entryinto said arrangement, the edges of the web 1 are firmly clamped by aclamping device 5, 6. The clamping device 5, 6 of the describedembodiment is comprised of two separate rows of base plates 3, 4 eachsupported by a respective chain link system that runs in tracks whichare not shown in the Figures. As will be seen from FIG. 9, each baseplate 3, 4 supports, via a support arm, a lever 7 which functions toclamp the edges of the web 1 firmly between itself and respective baseplates 3, 4 through the action of a spring force. The levers 7 areself-locking, implying that the clamping force that holds the web 1firmly to the base plates will increase as the material 1 is stretchedin the transverse direction T. The clamping device is represented byarrows in FIG. 3.

Subsequent to the edges of the web 1 having been clamped firmly in theaforedescribed clamping device 5, 6, the tracks that guide the links inthe chain link system diverge in the manner apparent from FIG. 1. Theweb 1 is thereby stretched successively in the transverse direction T.The links in the chain link systems then run parallel with one anotherand also parallel with the feed direction. In order to prevent the edgesof the web 1 from being subjected to twisting forces as a result ofdirectional changes of the base plates when entering and exiting thoseparts of the clamping device that are divergent and parallel relative tothe feed direction, the levers 7 may be provided with abutment bodies 8,said bodies being rotatably carried at the abutment ends of the lever 7and produced from a material that exhibits high friction to the materialin the web 1. However, this is not normally necessary, since theflexible material to be stretched in the arrangement is able to take-upthe small directional changes concerned relatively easily.

The clamping device 5, 6 may, for instance, be comprised of a chain linksystem from Flexlink, which includes two chains whose links carry thebase plates 3, 4. In the illustrated case, each chain has a length ofabout 5 m and is provided with 75 base plates. The levers 7 on the baseplates are normally closed and spring-biased. The length of chain may,of course, be chosen in accordance with requirements.

It will be understood that the invention is not restricted to theaforementioned stretching arrangement, and that other types ofstretching arrangements may be used. For instance, there is described inEP-A1-0 443 244 a stretching arrangement that includes two wheels whichare obliquely positioned in relation to each other and which areintended for stretching elastic film. The elastic film enters the wheelsat a point where their mutual spacing is small and leaves the wheels ata point where their mutual spacing is large, therewith stretching theelastic film.

Subsequent to having stretched the web 1 to a desired extent, a web ofmaterial 9, 10 is applied to respective opposite sides of the web 1, asbest seen from FIGS. 2 and 4.

The webs 1, 9, 10 then pass through an ultrasound welding unit 11 thatincludes a horn 12 and an anvil roll 13. The anvil roll 13 extendstransversely across the combined webs of material and includes tworegions of outwardly projecting anvils which are axially separated andsymmetrically located relative to the longitudinal symmetry line A-A ofthe web 1. The anvils in these regions are comprised of axiallyseparated rows of projections that extend peripherally around thecircumference of the anvil roll 13. Thus, subsequent to having passedthe ultrasound welding unit 11, the webs 1, 9, 10 are joined together intwo mutually separate zones 14, 15 that extend in the feed direction, asevident from FIGS. 1 and 5. The ultrasound welding unit is convenientlydriven in the manner described in EP-A1-0 494 941, so that the webs 9,10 will be joined together through holes in the web 1. The manner inwhich welding is effected is well known to the person skilled in thisart and will not therefore be described in more detail.

FIG. 5 illustrates the manner in which the sheets are joined togetherafter having passed the ultrasound welding unit 11. The sheets arejoined together over the whole of their respective surfaces, with theexception of a centre zone 16 and edge zones 17, 18. In the illustratedcase, the width of the centre zone 16 corresponds to a third of the fullwidth, whereas the edge zones 17, 18 correspond roughly to one-tenth ofthe full width. The width of the regions that shall be joined togetherwill depend on the application concerned and will thus vary.

After having been joined together in the zones 14, 15 as they passthrough the ultrasound unit 11, the webs 1, 9, 10 pass a dividing device19. The dividing device 19 is comprised of an ultrasound welding unitthat includes a horn 20 which coacts with an anvil roller 21 thatincludes outwardly projecting anvils 22 arranged in a semicontinuouspattern, as shown schematically in FIG. 10. By semicontinuous pattern ismeant here a surface whose topography is so configured that one pointacross the width of the pattern will always abut the ultrasound horn,whereas any chosen peripheral circumference line will exhibitdiscontinuous abutment with the ultrasound horn. Patterns of this typecan be produced, for instance, with a knurling process, although othermanufacturing processes may be used, such as milling, sparking oretching. The pattern is adapted to the desired perforation of the web 1and so that the distance between adjacent perforations will be so smallas to enable the elastic force in the stretched web 1 to pull the webapart in each region between two perforations. The perforations areformed as the three webs 1, 9, 10 move together through the gap or nipbetween the horn 20 and the outwardly projecting anvil 22. Ultrasoundenergy is transmitted to the three webs 1, 9, 10 at those points wherethe semicontinuous pattern 22 lies against the ultrasound horn 20.Because the intermediate web 1 is elastic and is in a stretched state,the amount of ultrasound energy that the web can store is smaller thanthe amounts of energy that can be stored by the non-loaded webs 9 and 10on respective sides of said intermediate web 1, meaning that theultrasound welding unit can be operated so as to perforate solely theintermediate, stretched web 1. As the elastically stretched web 1absorbs the energy to which it is subjected by the up and down movementsof the ultrasound horn, two different phenomena can cause the web torupture locally. There either occurs a local rise in temperature thatsoftens the elastic web 1 and the tensile force in surrounding parts ofthe web draw-in towards themselves softened material so as to create aperforation. Alternatively, the ultrasound energy assists in causing thematerial in the elastic and stretched web 1 to become brittle as aresult of so-called visco-elastic inertia, and thereby rupture at thepoint of perforation. A combination of these phenomena is, of course,also conceivable. The webs 9, 10 are also subjected to ultrasound energyin conjunction with perforation of the web 1. The webs 9, 10, however,are not subjected to load and are therefore able to absorb more of theenergy delivered without rupturing. However, these webs will also besoftened by the ultrasound energy delivered and therewith be joinedtogether in the perforation openings of the web 1 immediately after saidopenings have been formed in the aforedescribed manner. Because thedistance between mutually adjacent perforations is small, the materialin the elastic web 1 between the latest created openings and nearestpreceding openings will be torn apart by the tensile force in thestretched elastic material immediately after the opening has beenformed. Subsequent to having been divided, the web 1 will contractwithin the centre zone 16 to a totally relaxed state, which means that alarge central part of the centre zone 16 will consist solely of twosheets or layers subsequent to said division. FIG. 6 is a schematicillustration of the webs 1, 9, 10 subsequent to their passage throughthe dividing device 19.

Alternatively, the anvil pattern on the anvil roll may be discontinuousinstead of semicontinuous. It is also possible to use a fully continuouspattern, although in this latter case there is a serious risk of thewebs 9, 10 also being divided, as these webs are subjected to thetensile force in the elastic web 1 in those zones 14, 15 in which thethree webs are mutually joined, subsequent to division of the web 1. Itis therefore preferred to use an anvil roll that has a semicontinuousanvil pattern.

It will be understood that much less energy is required to perforate thestretched elastic web 1 than that consumed in perforating the webs 9,10. The amount of energy consumed in perforating the web 1 will dependon the choice of elastic material and the extent to which the elasticmaterial is stretched. Thus, it is possible to drive the dividing device19 so that the energy delivered to the webs 9, 10 will not be highenough to cause local melting of these webs in the division process butsufficiently high to cause perforation of the elastic web 1, wherewiththe webs 9, 10 remain unconnected with each other subsequent to dividingthe elastic web 1.

Subsequent to the webs 1, 9, 10 have passed the dividing device 19, theypass an ultrasound welding unit 22 positioned in the centre zone 16.This unit includes a horn 23 that coacts with an anvil roll 24 whichincludes outwardly projecting anvils that are conveniently comprised ofperipheral rows of projections so as to achieve punctiform welding ofthe centre zone 16. The unit 22 shall be placed at a distance from thedividing device 19 such that the parts of the web 1 situated in saidcentre zone will have had time to contract fully before the webs 1, 9,10 are joined together in the centre zone 16. Subsequent to havingpassed the unit 22, the webs 1, 9, 10 will be joined together also inthe centre zone, as shown schematically in FIG. 7.

Subsequent to this joining of the webs 1, 9, 10 in the centre zone, thetracks carrying the chain links converge towards each other, therewithcausing the edges of the webs to be moved closer to each other andtherewith allow the web 1 to contract in the zones 14, 15 in which theweb 1 is still stretched, and in the edge zones 17, 18. Contraction ofthe web 1 in the zones 14, 15 causes the webs 9, 10 to be pleated intosoft folds. When the distance between the edges has reduced to such anextent that the web 1 is moved in a generally relaxed state with notension, the levers 7 of the clamping device are caused to swing upwardsand therewith release the edges of the web 1.

In the case of the embodiment illustrated in the Figures, the webs 1, 9,10 are then joined together in the edge zones 17, 18 by means of anultrasound welding unit 25 and the webs will have the configurationshown in FIG. 8 after having passed the unit 25. Should it be found thatafter being released by the levers 7 those parts of the web 1 situatedin the edge zones do not contract to an extent sufficient for said partsto lie flush with or inwardly of the outer edges of the webs 9, 10, thelaterally outward projecting parts of the web 1 are suitably cut away.Edge welding is not absolutely necessary, since the mutually joined websare intended to be used in the manufacture of fastener tabs, wherewiththe edge zones 17, 18 form those parts of the tabs that are fixedpermanently to absorbent articles, meaning that the sheets or layers ofmaterial can be mutually joined in said edge zones in conjunction withfastening such a tab to an absorbent article.

Welding of the centre zone 16 can alternatively be effected after theweb 1 has been caused to relax to a tensionless state and its edgesreleased, therewith enabling edge and centre welding to be effectedsimultaneously.

Neither is it absolutely necessary to control contraction of the web 1subsequent to joining together the webs in said centre zone, since theclamping device can be constructed to release the edges of the webimmediately after the webs have been joined in the centre zone. Abruptrelease of the webs, however, may cause the composite web formed by saidthree webs to be pleated or puckered in an undesirable fashion and istherefore not preferred.

As the mutually joined webs 1, 9, 10 leave the aforedescribedarrangement, the webs are rolled onto a storage reel 26 or transferredto a process line in which absorbent article fastener tabs are producedfrom the basic starting material manufactured in the aforedescribedarrangement, said process line possibly being integrated with a processline for the manufacture of absorbent articles.

Such a process line may include, for instance, the application ofmutually separated and longitudinally extending strings of male orfemale elements, such as strings of hook elements in a so-calledtouch-and-close fastener, whereafter mutually opposing fastener tabs arecut from the thus formed web in pairs.

It will be understood that the inventive arrangement may include moredividing devices and welding units than those inferred above, so as toenable more elastic zones corresponding to zones 14-16 to be formed. Insuch arrangements, it may be suitable to support the webs at their outeredges so as to ensure that the composite web will not move laterally asthe stretched web is divided in each region between two elastic zones.Such supports may have the form of wheels or co-running belts. FIG. 11is a cross-sectional view of a web of material that has four zonescorresponding to the zones 14, 15 and three zones corresponding to thecentre zone 16. Such a web can then be divided into two webscorresponding to the web manufactured by means of the inventivearrangement illustrated in FIGS. 1-10.

FIG. 12 illustrates schematically and in perspective a section of basicstarting material intended for the manufacture of absorbent articlefastener tabs and produced by means of the arrangement shown in FIGS.1-10, said starting material having a length L, a cross width T, twoelastic sheets 1 and at least two further sheets 9, 10, which arepreferably comprised of nonwoven material. The sheets 1, 9, 10 arejoined together in the aforedescribed manner, such as to form two zones14, 15, two edges 17, 18 and a centre zone 16. The zones 14, 15 areelastic in the cross-direction T, whereas remaining zones arenon-elastic, by virtue of the fact that the sheets 9, 10 are comprisedof a generally unstretchable material. The relationship betweentransversal extension of the elastic zones in a maximum stretched stateand in a relaxed state is less than or equal to the ratio of thetransverse extension of the intermediate non-elastic zone to the sum ofthe transverse extension of those pieces of elastic material that extendinto said zone, since the elastic material is able to contract freely inthe non-elastic zone while part of the force for contracting thenon-elastic sheets 9, 10 is consumed in the elastic zone, andconsequently the elastic material will remain somewhat stretched in theelastic zone.

Fastener tabs can be produced readily from the basic starting material,by fastening longitudinally extending and mutually separated strings 27,28 of hook elements onto the material in the centre zone 16, andthereafter cutting right-hand and left-hand fastener tabs from thematerial. FIG. 13 shows schematically how fastener tabs can be cut-outso as to enable the starting material to be used without any appreciablewastage. The material is first cut along a line 30 that has a modifiedsquare-wave shape and which extends in the longitudinal direction L ofthe starting material in the centre of the zone 16, whereafter cuts aremade along a sequence of cutting lines 29 that extend in thecross-direction T of said material from said respective edges thereof upto the longitudinal line 30, such that each line 29 intersects a wavecrest or wave trough of the undulating line 30 in its centre. Thecutting lines 29 on respective sides of said longitudinal line 30 areoffset relative to each other through a distance corresponding to onehalf wavelength, so that the sequence of cutting lines 29 on one side ofthe cutting line 30, e.g. the right-hand side in the Figure, eachintersect wave crests, whereas the cutting lines on the other side ofthe cutting line 30, the left-hand side in the Figure, each intersectwave troughs. As will be seen from FIG. 13, pairs of left-hand andright-hand fastener tabs will be cut from the starting material in thisway, wherewith the tabs in each pair of tabs are offset relative to oneanother in the longitudinal direction of said material.

It is, of course, possible to use other regular wave shapes for thecutting line 30, e.g. a sinusoidal wave or a purely square wave shape.

FIG. 14 illustrates schematically one such fastener tab 31 which has acontinuous layer of material that includes a central elastic part 32 andtwo non-elastic parts 33, 34, of which the part 33 is themanufacturer-end of the tab 31 and is intended for attachment to oneside portion of an absorbent article, such as a diaper. The othernon-elastic part 34 is located at the user end of the tab, i.e. the endof the tab which is gripped by the wearer in order to fasten togetherthe side portions of a donned diaper. The central elastic part 32 isformed so as to be elastic in the transverse direction T and essentiallynon-elastic in the longitudinal direction L.

The non-elastic part 34 is conveniently provided with some form offastener elements 27′, particularly such that can be “firmly locked” andthen “unlocked”. Examples of suitable fastener elements include male orfemale parts of touch-and-close fasteners, buttons, or the like, whichare intended to coact with complementary elements provided on theoutside of the diaper. It is also possible to use adhesive or cohesivebinding agents as fastener elements.

Diapers often include an outer sheet of nonwoven material to whichcertain types of hook elements can readily fasten, and it is thereforebeneficial to use fastener elements 27′ in the form of such hookelements. It is also possible to provide the diaper with special loopelements to which the fastener elements 27′ can be coupled.

Although the fastener tabs 31 have been shown to have a generallyrectangular shape, it will be understood that the tabs may have anyother suitable shape.

Although the invention has been described above with reference to adiaper, it will be understood that the invention is not restrictedthereto and can be applied with any type of absorbent articlewhatsoever.

In order to provide the wearer of the diaper with a high degree ofcomfort, it is suitable for the fastener tabs to have a given stiffness,particularly in the longitudinal direction L. It is also important thatthe tabs will not chafe the wearer. The non-elastic material is suitablychosen so that the laminate will have sufficient stiffness while, at thesame time, being soft and gentle against the wearer's skin. Thismaterial will preferably be a nonwoven material.

An example of suitable non-elastic material is 20 grams spunbond(nonwoven) and 30 grams spunbond (nonwoven) as material layers,preferably two nonwoven layers containing thermoplastic fibres, e.g.polypropylene fibres.

The thinner nonwoven layer (20 grams) is softer and is placed suitablyagainst the wearer's skin. The thicker layer (30 grams) providesstiffness. The use of different thicknesses enables the fastener tabs tobend when applied to an absorbent article. The fastener tab foldsautomatically towards the thinner nonwoven layer, by virtue of the factthat the elastic layer disposed between the nonwoven layers and mountedin a stretched state is able to contract more to that side on which thethinnest layer of nonwoven is fastened. The fastener element 27′ willtherefore preferably be fastened to the thinnest nonwoven layer. This isbeneficial when the fastener tab shall be secured to the diaper andfolded in towards/against the inside of said diaper.

The elastic layer or sheet 1 may consist of elastic film, elastic foam,elastic net material or of a laminate that includes at least one elasticcomponent.

FIG. 15 illustrates schematically a diaper 35 whose side portions havebeen fastened together with the aid of fastener tabs 31 of the kindshown in FIG. 14.

Absorbent articles normally include a surface sheet, anacquisition/transport sheet, a rear liquid-impermeable sheet, or backingsheet, and an absorbent body. The acquisition/transport sheet may becomprised of a high loft material. The absorbent body of such productsmay be made of cellulose pulp. These layers or sheets will not bedescribed in more detail, since they are well known to the personskilled in this art.

It will be understood that the described embodiments can be modified inseveral ways within the scope of the invention. For instance, the anvilroll 13 may be comprised of two or more separate rolls that each coactwith its individual ultrasound horn. Moreover, joining of the webs inthe different zones, and for thermoplastic materials also the divisionof the stretched web 1, may be effected by means of heat welding unitsinstead of ultrasound welding units. Heat welding can be accomplishedwith the aid of a high mechanical pressure in addition to heated rollersor the like. The webs may also be joined together with the aid of gluingunits instead of ultrasound welding units. Furthermore, there may beused anvil patterns other than the described rows of projections, and itis also possible to use patterns other than a semicontinuous pattern onthe anvil roller in the dividing device. Although it is preferred to useessentially non-stretchable material in the material webs to which thestretched web is joined, it will be understood that it is also possibleto use elastic material in these webs instead when wishing to producematerial that has different degrees of elasticity in different zones.Although the elastic web is divided centrally between the elastic zonesin the illustrated embodiment, it will be understood that the dividingline may be placed closer to one elastic zone than to the other. Theinvention is therefore restricted solely by the contents of theaccompanying claims.

1. A fastener tab (31) intended to be fastened to one side portion of anabsorbent article that includes a front part, a rear part and anintermediate crotch part, so as to join together coacting side portionsof the front and rear parts of said article, said fastener tabs having auser end and a manufacturer end spaced apart a first distance when thefastener tab is unstressed, characterised in that the fastener tab (31)includes a layer of elastic material (1) which is mounted on andfastened in a stretched state in which the user end and the manufacturerend are spaced apart a second distance greater than said first distance,to two layers (9, 10) of essentially unstretchable material; in that thetwo unstretchable layers extend beyond the elastic layer to form anunstretchable end-part (34) that includes the user end; in that theelastic layer (1) extends in a relaxed state only partway into theunstretchable end-part (34); and in that fastener elements (27′) aremounted on the unstretchable end-part (34) on one of said twounstretchable layers (9, 10), a part of the end-part (34) being withoutthe elastic layer.
 2. A fastener tab according to claim 1, characterisedin that the unstretchable layers (9, 10) are comprised of nonwovenmaterial of mutually different weights per unit area; and in that thefastener elements (27′) are mounted on the outside of the nonwoven layerthat has the lowest weight per unit area.
 3. An absorbent articlecharacterized in that said article includes a fastener tab according toclaim
 1. 4. An absorbent article characterized in that said articleincludes a fastener tab produced from starting material having at leasttwo elastic zones (14, 15) which extend in the longitudinal direction(L) of said material and which are mutually separated in thecross-direction (T) by an intermediate non-elastic zone (16); elasticmaterial (1) extending from the elastic zones (14, 15) only partway intosaid non-elastic zone (16); the elastic zones (14, 15) including a sheetof elastic material (1) which is mounted in a stretched state in saidcross-direction (T) between two sheets of material (9, 10) and fastenedthereto; and said two sheets of material (9, 10) extending over eachelastic zone (14, 15) and said non-elastic zone (16), a part of saidnon-elastic zone being without elastic material.